At least 15 dead, 30 injured after New Orleans truck ramming attack; New questions about physical security measures after New Orleans truck attack; Louisiana Attorney General says Airbnb fire near New Orleans attack linked to production of explosives; and more on tonight's broadcast.

Police uncover messages from the suspect that may show a motive in the Las Vegas Cybertruck explosion as his ex-girlfriend shares new video with NBC News, federal authorities warn of potential copycat attacks after the deadly New Orleans attack, a massive snowstorm set to hit the U.S., and more in tonight's broadcast.